Chapter 11, Problem 14PS

A transportation strategist wanted to compare the traffic congestion levels across four continents: Asia, Europe, North America, and South America. The file CongestionLevel contains congestion level, defined as the increase $\left(\text{\%}\right)$ in overall travel time when compared to a free flow situation (an uncongested situation) for 10 cities in each continent.

a. At the 0.05 level of signification, is there evidence of a difference in the mean congestion level across continents?

b. if the results in (a) indicate that it is appropriate to do so, use the Tukey-Kramer procedure to determine which contains differ in congestion level

c. What assumption are necessary in (a)?

d. At the 0.05 level of significance, is there evidence of a difference in the variation of the congestion level across continents?